Method and system for setting rates and targets in a range management system

ABSTRACT

A method and apparatus comprises determining a number of planned starts of a product during a predetermined time period for future processing, averaging the number of planned starts for the predetermined time period, and setting a production rate for a first range based on the average number of planned starts.

FIELD OF THE INVENTION

The invention relates to the manufacture of integrated circuits, andmore particularly, to a system and method for controlling work inprogress.

BACKGROUND DESCRIPTION

Semiconductor manufacturers are continually working to reducetime-to-market in an effort to improve serviceability while decreasingoperating costs. Therefore, efforts have been made to develop andimplement systems and methods such as continuous flow manufacturing,including operations management, which is also known as rangemanagement.

In a standard range management system, wafer processing operations arepartitioned into a series of flows, where the products in each flowfollow similar routings through the fabricator (fab). These flows aredivided into ranges, where the expected cycle time of the work inprogress (WIP) in each range is 24 hours. For example, a range mayinclude the following operation sequence: lithography, metrology,overlay, and metrology CD.

In a range management system, each range has a daily takt rate (DTR)which is the ideal daily throughput rate for that range. Takt is aGerman word for “beat” and represents the pace at which product movesthrough the manufacturing process. In a standard range management schemedaily takt rates (DTRs) are static, changed infrequently, and set at aconstant level across all ranges in a product flow.

Daily output targets for each range are set based on the DTR and alsothe amount of WIP in the range, and the amount of WIP in the next range.A standard range management matrix exists, that is used to determine thedaily output targets. For example: the daily output target could beanywhere from zero, if the next range WIP is greater than 2.5× the DTR,to 1.25× the DTR if the next range WIP is lower than the DTR. When arange meets the target output for a day, the range is “stopped,” so thateffort can be directed towards other lots, in ranges that still need toachieve the target output. In a standard range management system,targets are set once per day.

At the end of each day, the performance of each range is evaluated andcompared with the target to identify problem areas. By operating themanufacturing line with this methodology, the WIP stays balanced andresources are evenly distributed.

The evaluation of targets only once a day, though, can cause problemsdue to the movement of WIP within the day. The WIP profile changesfrequently, such that, to ensure WIP balance, some stopped ranges mayneed to be activated and conversely, ranges that are delivering WIP intoover-WIP ranges may need to be stopped so that resources can be appliedto move other WIP into under-WIP ranges.

In existing range management schemes, WIP is driven to conform to astatic DTR profile. For example, even though a certain product may onlybe ramping up, the DTR is set at a flat rate across all ranges. Theresult is that the WIP is forced quickly through certain ranges, becausethey seem to be under-WIP, and stopped in other ranges to divertresources. This does not reflect the commits, and ignores the capacityof different parts of the line. In such situations, WIP is driven atvarying rates, but is not produced at committed rates.

Accordingly, there exists a need in the art to overcome the deficienciesand limitations described hereinabove.

SUMMARY OF THE INVENTION

In a first aspect of the invention, a method comprises determining anumber of planned starts of a product during a predetermined time periodfor future processing, averaging the number of planned starts for thepredetermined time period, and setting a production rate for a firstrange based on the average number of planned starts.

In another aspect of the invention, a system comprises a deviceconfigured to store current range matrix data, determine results basedon the inputted current range matrix data, and update a production ratefor at least a first range based on the results.

In another aspect of the invention, a computer program productcomprising a computer useable medium including a computer readableprogram, wherein the computer readable program, when executed on acomputer, causes the computer to determine a number of planned starts ofa product during a predetermined future time period, average the numberof planned starts for the predetermined future time period, and set aproduction rate for a first range based on the average number of plannedstarts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an environment for implementing an aspect of the invention;

FIG. 2 is an illustrative example of the sequence of operations in aflow;

FIG. 3 is an illustrative example of the distribution of work inprogress in ranges along a flow;

FIG. 4 is a flow chart illustrating steps in accordance with theinvention;

FIG. 5 is a flow chart illustrating steps in accordance with theinvention; and

FIG. 6 is a flow chart illustrating steps in accordance with theinvention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention provides a system and method for setting taktrates via production starts and capacity in a range management system.In the invention, for each range within a flow, takt rates arereflective of start rates, which are determined based on customerdemands, product ramps, and capacity of the manufacturing process.Additionally, the daily output targets are reassessed periodically, in apreferred embodiment, every twelve hours. In embodiments, the updateddaily output targets are automatically communicated to the real-timedispatching system, where the priority of lots is changed accordingly.

In today's dynamic manufacturing environment, production start profilescan change daily, or even more frequently. A dynamic takt rate,reflective of starts, could produce a noisy and erratic profile and addvariability to the system. To prevent such an effect, the inventionprovides a damping system by setting takt rates to be the average ofsome previous period, for example, the previous week. The inventionmatches the frequency of takt rate changes to the frequency of the startprofile changes (e.g. hourly, daily, weekly, or monthly).

Since the takt rates vary by range as well as by flow, the inventionfurther provides a method to “move” the rates on a daily basis to matchthe movement of work in progress (WIP) through the manufacturingprocess. The invention therefore provides a fast, proactive, andautomated mechanism to set takt rates for a complex, on-demandmanufacturing environment.

With reference to the accompanying drawings, FIG. 1 shows anillustrative environment 30 for managing the processes in accordancewith the invention. To this extent, the environment 30 includes acomputer infrastructure 32 that can perform the processes describedherein. In particular, the computer infrastructure 32 is shown includinga computing device 34 that comprises a rate setter 36, which makescomputing device 34 operable to perform the processes described herein.The computing device 34 is shown including a processor 38, a memory 40,an input/output (I/O) interface 42, and a bus 44. Further, the computingdevice 34 is shown in communication with an external I/O device/resource46 and a storage system 48. As is known in the art, in general, theprocessor 38 executes computer program code, which is stored in memory40 and/or storage system 48. While executing computer program code, theprocessor 38 can read and/or write data, such as the rate 50, to/frommemory 40, storage system 48, and/or I/O interface 42. The bus 44provides a communications link between each of the components in thecomputing device 34. The I/O device 46 can comprise any device thatenables an individual to interact with the computing device 34 or anydevice that enables the computing device 34 to communicate with one ormore other computing devices using any type of communications link.

In any event, the computing device 34 can comprise any general purposecomputing article of manufacture capable of executing computer programcode installed thereon (e.g., a personal computer, server, handhelddevice, etc.). However, it is understood that the computing device 34 isonly representative of various possible equivalent computing devicesthat may perform the processes described herein. To this extent, inother embodiments, the functionality provided by computing device 34 canbe implemented by a computing article of manufacture that includes anycombination of general and/or specific purpose hardware and/or computerprogram code. In each embodiment, the program code and hardware can becreated using standard programming and engineering techniques,respectively.

Similarly, the computer infrastructure 32 is only illustrative ofvarious types of computer infrastructures for implementing theinvention. For example, in one embodiment, the computer infrastructure32 comprises two or more computing devices (e.g., a server cluster) thatcommunicate over any type of communications link, such as a network, ashared memory, or the like, to perform the process described herein.Further, while performing the process described herein, one or morecomputing devices in the computer infrastructure 32 can communicate withone or more other computing devices external to computer infrastructure32 using any type of communications link. In either case, thecommunications link can comprise any combination of various types ofwired and/or wireless links; comprise any combination of one or moretypes of networks (e.g., the Internet, a wide area network, a local areanetwork, a virtual private network, etc.); and/or utilize anycombination of various types of transmission techniques and protocols.As discussed herein, the rate setter 36 enables computer infrastructure32 to set the rate 50.

FIG. 2 is an illustrative example of the sequence of operations in aflow. In the figure, WIP moves along the flow, from left to right, aseach operation is completed. For example, as a wafer moves through thefab, it will move from lithography 100, to metrology 110, to overlay120, to metrology CD 130, etc. In this example, a first range mightinclude only the operations 100-130, and a second range might includeoperations 140 and 150.

The present invention addresses the problem of static takt rates, bydynamically setting the takt rate based on the production starts, asshown in FIG. 3. That is, while production is ramping up, for example inrange 1, the takt rate is set lower; but when production is up to speed,for example in range 25, the rate is set at capacity. In this manner,the performance of each range is assessed under more realistic goals,and the fab resources are more efficiently allocated.

FIG. 4 is a flow chart illustrating steps in accordance with theinvention. The steps of FIG. 4 (as well as any other flows) may berepresentative of a high-level block diagram implementing the stepsthereof. The present invention can take the form of an entirely hardwareembodiment, an entirely software embodiment or an embodiment containingboth hardware and software elements, or the invention can be executedentirely or partially manually. In a preferred embodiment, the inventionis implemented in software, which includes but is not limited tofirmware, resident software, microcode, etc. Furthermore, the inventioncan take the form of a computer program product accessible from acomputer-usable or computer-readable medium providing program code foruse by or in connection with a computer or any instruction executionsystem. For the purposes of this description, a computer-usable orcomputer readable medium can be any apparatus that can contain, store,communicate, propagate, or transport the program for use by or inconnection with the instruction execution system, apparatus, or device.The medium can be an electronic, magnetic, optical, electromagnetic,infrared, or semiconductor system (or apparatus or device) or apropagation medium. Examples of a computer-readable medium include asemiconductor or solid state memory, magnetic tape, a removable computerdiskette, a random access memory (RAM), a read-only memory (ROM), arigid magnetic disk and an optical disk. Current examples of opticaldisks include compact disk-read only memory (CD-ROM), compactdisk—read/write (CD-RW) and DVD.

In embodiments, at Step 410, the future starts are predicted. In thisstep, the number of planned starts for each part number is determined,for example, from a database. The number of planned starts will be forsome future period, for example, in the next week. At Step 420, thesepart numbers are mapped to their corresponding range flows. That is, thenumber of starts is determined for each flow. At Step 430, all plannedstarts within each flow are summed. At Step 440, the rate in range 1 ofeach flow is set to the average number of starts for that flow. At Step450, the rate in the nth range is set to the takt rate for the previousday in the (n−1)th range; this process is repeated for each range in theflow. If necessary, for example based on business needs, the takt ratemay be set by manual override at Step 460. This process is repeated foreach flow in the fab.

The following is an illustrative example of the present invention.Referring to the tables below, in Table 1, the average number of startsper week is calculated by part number for a particular week, e.g., theweek of April 2002. In this step, the average calculated number for eachpart number is then assigned as the daily takt rate. TABLE 1 Date PartApril April April April April April April Aver- # 2002 2003 2004 20052006 2007 2008 age AXXXX 25 25 25 0 25 25 0 17.9 BXXXX 0 0 0 25 0 0 03.6 CXXXX 0 25 25 0 0 0 0 7.1 DXXXX 0 0 0 0 50 50 50 21.4 EXXXX 25 25 2525 25 25 25 25.0 FXXXX 25 0 0 25 0 0 0 7.1 GXXXX 50 50 50 50 25 25 2539.3

In Table 2, the part numbers are mapped to their respective flows, forexample, part numbers AXXXX, BXXXX, and CXXXX are in flow ABC.Therefore, the number of starts for flow ABC is the sum (rounded up) ofthe starts for these part numbers. TABLE 2 April April April April AprilApril April 2002 2003 2004 2005 2006 2007 2008 Flow ABC 29 29 29 29 2929 29 Flow DEFG 93 93 93 93 93 93 93

In Table 3, the takt rates are propagated daily towards the right. Thatis, for example, on day one, the takt rate for range 1 will be set tothe average starts, but on day two, the takt rate for range two will beset to the takt rate of range 1 set on day one, etc. TABLE 3 range FlowABC 1 2 3 4 5 6 7 day 1 29 30 30 30 30 30 30 day 2 29 29 30 30 30 30 30

In Table 4, a user can manually override the takt rate for any range.This override (marked in the table with boxes) can persist until withoutfurther manual setting. In the example, the overrides propagate to theright daily, as any other takt rate does. TABLE 4

The table below is an example of a range matrix in accordance with thepresent invention. In this matrix, DTR is the daily takt rate, RTR isthe recovery takt rate (DTR plus 25%), and MTR is the minimum takt rate.For example, a snapshot of WIP is taken, and the range matrix is used toevaluate the range targets. If a range has been stopped, then the targetis reevaluated after a period of time, for example, after twelve hours.If the WIP position has changed, as determined by the range matrix, thenthe range is assigned a target greater then zero. Since only half theday is remaining, the range target is based on WIP in the last half ofthe range, which is equivalent to half a day's cycle time. This sets arate that is achievable in the remaining twelve hours. 1. If WIP in your2. And your WIP is: customer's range is: =>RTR <RTR 3. Then process: 3.Then process: <RTR WIP in last half of WIP in last half of range to RTRrange to RTR RTR to (2 × DTR) WIP in last half of WIP in last half ofrange to DTR range to DTR (2 × DTR) to WIP in last half of Stop. (2 ×RTR) range to MTR >(2 × RTR) Stop. Stop.

Similar logic is applied for a range that is not stopped at the time ofthe snapshot. For all ranges that are not stopped, the normal rangematrix is used. If the range matrix produces a target of zero, nofurther output from the range is produced. Targets from all other rangesremain the same. The updated range targets are used to evaluate whethereach range successfully met its target.

In the table above, the current WIP and the takt rates (DTR and RTR) arethe data to be input, and updated daily targets are the outputs Forexample, if WIP in your customer's range is less than the recovery taktrate, and your WIP is greater than or equal to the recovery takt rate,the process WIP in the last half of the range, until the recovery taktrate is met.

FIG. 5 is a flow chart illustrating steps in accordance with theinvention. In embodiments, at Step 510, existing range data is input. AtStep 520, the daily target for each range is updated based on theresults of the range matrix (e.g., see above table). At Step 530, theupdated daily targets are output. This data may be output, for example,to a real-time dispatching system, whether automated or manuallycontrolled, or to a range management system.

FIG. 6 is a flow chart illustrating alternative steps in accordance withthe invention. In effect, these steps query whether a range is stoppedand should be restarted, or is running but should be stopped. Thisdecision is based upon the current range matrix (shown in the abovetable) data. In embodiments, at Step 610, the existing targets are inputfor each range. At Step 615, the system is indexed to the first range.At Step 620, a determination is made as to whether the range underconsideration is stopped, that is, whether the existing target is set atzero. If yes, then at Step 625, a determination is made as to whether,based on the current range matrix data, the range under considerationshould be re-started. If yes, then at Step 630, the target is updated tore-start that range. If the answer to either of the precedingdeterminations is no, then at Step 635, a determination is made as towhether the range under consideration is not currently stopped, that is,whether the existing target is greater than zero. If yes, then at Step640, a determination is made as to whether, based on the current rangematrix data, the range under consideration should be stopped. If yes,then at Step 645, the target is updated to stop that range. If theanswer to either of the preceding determinations is no, then at Step650, a determination is made as to whether the range under considerationis the last range in that flow. If no, then at Step 655, the system isindexed to the next range, and the process is repeated from step 620. Ifyes, then at Step 660, the targets are output. As discussed above, thisdata may be output for example to a real-time dispatching system,whether automated or manually controlled, or to a range managementsystem. The process is repeated periodically for all flows in the fab.For example, the process may be repeated every twelve hours. In thismanner, the performance of each range is assessed more frequently, thevariability of WIP is reduced, and the overall cycle time in the fab isimproved.

The method as described above is used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multi-chip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

While the invention has been described in terms of embodiments, thoseskilled in the art will recognize that the invention can be practiceswith modifications and in the spirit and scope of the appended claims.

1. A method, comprising: determining a number of planned starts of aproduct during a predetermined time period for future processing;averaging the number of planned starts for the predetermined timeperiod; and setting a production rate for a first range based on theaverage number of planned starts.
 2. The method of claim 1, furthercomprising setting a second production rate for a second range based inthe average number of planned starts.
 3. The method of claim 1, furthercomprising propagating the production rate of the first range to asecond production rate for a second range.
 4. The method of claim 1,further comprising repeating the determining, averaging, and settingsteps for a second predetermined time period in the future.
 5. Themethod of claim 4, wherein the second predetermined time period is asame amount of time as the predetermined time period.
 6. The method ofclaim 1, wherein the predetermined time period is one week.
 7. Themethod of claim 3, wherein the second production rate of the secondrange is based on the first production rate within a previous timeperiod.
 8. The method of claim 1, further comprising dynamicallyadjusting the production rate for the first range based on the averagenumber of planned starts.
 9. The method of claim 8, wherein theadjusting is provided on a predetermined schedule.
 10. The method ofclaim 1, further comprising manually overriding the production rate asprovided in the setting step.
 11. The method of claim 1, wherein thesteps of claim 1 are implemented on computer readable medium.
 12. Asystem comprising at least one device is configured to: store currentrange matrix data; determine results based on the current range matrixdata; and update a production rate for at least a first range based onthe results.
 13. The system of claim 12, wherein the current rangematrix data comprises current work in progress and current targets. 14.The system of claim 12, wherein the device determines results bycomparing current work in progress to current targets in order todetermine how much work is to be produced in a future time period basedon the current range matrix data.
 15. The system of claim 12, whereinthe steps of claim 12 are implemented on computer readable medium. 16.The system of claim 14, wherein the at least one device is configuredto: index to an nth range; determine whether an existing target is zero;determine whether the existing target should be greater than zero; andupdate the target based on the results of whether the existing targetshould be greater than zero.
 17. The system of claim 16, wherein the atleast one device is configured to: determine whether the existing targetis greater than zero; determine whether the existing target should zero;and update the target based on the results of the whether the existingtarget should zero.
 18. The system of claim 17, wherein the at least onedevice is configured to: determine whether the nth range is the lastrange; index to (n+1) range; determine whether the existing target iszero; determine whether the existing target should be greater than zero;and update the target based on the results of the whether the existingtarget should be greater than zero.
 19. The system of claim 17, whereinthe at least one device is configured to output the updated targets. 20.A computer program product comprising a computer useable mediumincluding a computer readable program, wherein the computer readableprogram, when executed on a computer, causes the computer to: determinea number of planned starts of a product during a predetermined futuretime period; average the number of planned starts for the predeterminedfuture time period; and set a production rate for a first range based onthe average number of planned starts.